The luxury-real-estate company Brown Harris Stevens said prices fell 23.1%, to $1.87 million, year-over-year. The Corcoran Group put the decline in the South Fork's median price at 11%.

Ernie Cervi, Corcoran's regional senior vice president, told the New York Post that the slump in activity late last year was related to uncertainty about the election. Consumer confidence has spiked since the election outcome became clear, which could revive the market this year, Cervi said.

Housing market activity in the Hamptons this year could also be tied to how Wall Street professionals perform, as it's a prime location for buying vacation homes. After Hamptons home sales fell in the third quarter, Jonathan Miller, CEO of the real-estate appraisal firm Miller Samuel, tied the drop to weak hedge-fund performance.

The fourth-quarter report prepared by Miller's firm showed a 7.2% drop in the median sales price of Hamptons homes compared with last year. The number of sales closed fell by nearly 15%, and it took longer for sales deals to close — about four extra days, compared with the same time last year.

At the luxury end of the Hamptons market, the median sales price fell 29.5%, to $5.85 million, year-on-year, according to Miller Samuel. But this did not deter developers from putting more homes up for sale, as inventory increased 21% in the same period.

The opposite is happening about 100 miles away in Manhattan, where fewer homes with overzealous prices are being offered for sale as more buyers push back.